Aircraft cooling valve



Nov. 6, 1951 J. E. ESHBAUGH ET AL 2,574,254

AIRCRAFT COOLING VALVE Filed Dec. 28, 1944 'Jmnentors as 565283 7162 u WZ7VZZ (Ittornegs Patented Nov. 6, 1951 -AIRCRAFT oooLrnG VALVE Jesse E. Eshbaugh and Nelson Walker, Flint, 'Mich.,'assignors to Genera'lMotors Corporation, Detroit, .Mich., azcorporation of vDelaware Application December 28, 1944, Serial .No. 570,149

I5 Claims. (01. '27 7-61) This invention relates to an improved heat transfer system and more particularly to a pressure control valve especially adapted for the liq- -uid cooling system of an airplane engine.

The operating temperature of an engine is :a factor for reliability and 'performance'and the efficiency of the cooling system is raised by closing v the interior from atmosphere and utilizing the heat expansion of the contents to place the cir- 'culating liquid under pressure. Thus'the boiling point of the liquid can beincreased and evaporapressure valve set to maintain a given pressure at sea level will blow off unfortunately'at a'much lower pressure in altitude flight or just when heat dissipation in the radiator is dependent on a relatively smaller air density and'c'alls 'for'increased pressure on the contents.

To meet the situation thefpresent invention involves the provision of an automatic control valve responsive to pressure difierentia1 but which is compensated for difierences both in altitude and system temperature.

In the accompanying drawing showing the control device in elevation and partly ,in section the reference numeral l indicates a coolinglsystern wall for the space or passageway 12 tocohtain the cooling liquid which circulates between the engine coolingjacketand the radiator.

the control unit. Interiorly of the .casingiissa shoulder 6,.preferably having a raisedannular rib aiiording a valve seat for an inwardly seatingor outwardly opening valve and when the valve is open the hollow. casing 5 providesa passageway for communicating the interior of the system with v .the exterior atmosphere through the reducedend portion 4 and an opening in the casing wall desirably in the form of a hollow lateral extension 1 to which may be joined ahose or'tubing leading to a convenient vent 'point.

Bypassing the main valve "to "relieve subatmospheric' pressure"within the *system'is apas- .On= the wall I is a threaded boss 3 to receivethe re- 1 duced end or nipple 4 of the hollow casing 5 of sage conveniently formed in the wall of the casingi and normally closed by an inwardly opening check valve 8. For the purpose of the by-pass the casing wall has an enlargement or thickened portion 9 containing drilled openings l0 and II with the lateral opening l0 entering the casing port below the valve seat 6 and being closed at its outer end by a plug l2 and the vertical opening ll joins the hole ill with a pocket 13 housing the outwardly seated valve 8 and its spring [4. Thevalve seats against a ring of rubber, fiberor other suitable material secured by a hollow rivet IS on the underside of a partition wall or fiat plate l6 which extends entirely across the top of the casing '5 under the removable cover or dome ll. One or more holes can be drilled through the partition IE to open the interior of the cover to atmospheric pressure within the casing 5. A centralopening in the partition [6 receives an axially extending dependent pin l8 threaded at its upper end for adjustable attachment with acollaror abutment head l9 which bottoms on the upper side of the partition 16 and seats one end of a coil spring 20 whose opposite end is located within and by the raised central portionof the domed cover IT. A set screw 2| removably threaded into the top of the dome projects downwardly and limits upward movement of the pin I 8 in its deflection of thespring 20. Removal 'of'the set screw 2| enables insertion of a screw driver into engagement with the slotted upper end of thepin l8 for its adjustment in the stop collar I9 to vary the length of the pin projection downwardly below the wall l6 and thereby control to a predetermined extent the relative move- "mentof the valve parts before the spring 2 El comes into action to resist further 'movement. The

upper end of the collar [9 is slotted as at 22 to 'j permit the collar to be pinched inwardly and contracted into tight frictional contact with the pin for insuring against accidental turning of the pin held closed by a coil spring 23 surrounding the 7 pin and hearing at opposite ends on the .abutment'seat and the underside of the partition wall 7 I6. Thus a predetermined movement of the abutment seat against the elastidforce of the --spi3ing *2 3- must take place to bring the abut- "merit sea-tinto contact with the'nose of the-pin before thrust can be transmitted through the pin for supplementing the resistance of the primary spring 23 by the added resistance of the secondary spring 20.

The pin abutment seat referred to consists of the base of a cup-shaped stamping 24 telescoped for compactness about the spring 23 and the dependent pin l8 and which cup together with a surrounding corrugated flexible wall or bellows 25, an enclosing shell 26 and a dependent dead end tube or bulb 21 constitute the main parts of the floating valve normally seated on the shoulder 6 to seal the engine cooling system. The large diameter upper shell 26' above the valve seat 6 and the smaller diameter lower tube projected below the valve seat may be considered as a one-piece unit, but for convenience of manufacture they are shown as separately formed parts soldered together between the intumed annular flange at the bottom of the shell and the outturned annular flange at the top of the tube and which flanges afford an intermediate shoulder to seat on the casing shoulder 6. A seal- .ing gasket 28 is positioned under the intermediate casing shoulder by a flanged sleeve 29 press fitted or soldered on the wall of the tube :21. The inside of the intermediate shoulder, through the outturned flange of the tube 21, has fastened securely thereto the lower end of the expansible bellows 25, whose opposite or free end is secured to an annular outturned flange of the cup 24 which affords a header closing the interior chamber of the bellows. Maximum expansion of the bellows is limited by an abutment ring 30 carried at the top of.

the shell 26 for contact with the outturned flange of the cup 24. Contraction of the bellows is limited by contact of the base of the cup or header 24 with a ported and flanged bushing 3| fitted to the intermediate shoulder and with-l in the top of the dependent tube 21. Raised radial ribs on the upper surface of the bushing 3| seat the bottom of the cup 24 and afford between them openings to insure communication at all times of the bellows chamber through the ported bushing 3| with the chamber interiorly of the tube 21. This chamber space is about two-thirds filled with liquid of a type whose boiling point substantially corresponds with the coohng system liquid. For convenience the same liquid solution can be used and the liquid is introduced prior to installation through .an opening in the bottom of the tube, the open- ;ing thereupon being sealed by the plug 32.

In the event system internal pressure decreases below atmospheric pressure then external :air pressure will unseat the by-pass valve 8 as :the small force of the light spring is overcome :for substantially balancing the pressures. Internal system pressure in excess of external pressure will act on tthe underside of the outwardly opening valve to lift it from its seat 6. With the parts positioned as illustrated the differential pressure needs to overcome the downward force exerted by the primary spring 23. A drop in external pressure, as occurs in flight from sea level to higher altitude, will be compensated for by bellows expansion since pressure within the bellows acting on the underside of the header 24 will exceed external pressure on the upper surface of the header. Expansion of the bellows deflects the spring 23 and Thus even though the differpressure will be substantially unaffected by the drop in external pressure.

The bellows will respond not only to variations in atmospheric pressure but also to system temperature changes inasmuch as the dependent dead end tube 21 projects a considerable distance below the closure valve and exposes a large wall area to the system contents within the space 2 for the transfer of heat between the system liquid and the liquid interned within the bellows and its bulb chamber. Thus vapor pressure within the bellows tends to expand the bellows against the resistance of both the spring force and the external atmospheric pressure and the extent of expansion for a given bellows pressure will depend upon the value of external pressure so that changes in both temperature and altitude are compensated for in the operation of the valve in controlling the system operating pressure for the different operating conditions.

With temperature compensation the cooling system will not be subjected to any higher differential pressurethan is necessary to produce adequate cooling whereas conventional valves heretofore used have been designed to relieve at a given high pressure and therefore pressure builds up although the temperature condition of the engine may not require the higher pressure for cooling purposes. Considering that the primary spring 23 can be overcome by a system pressure of seven pounds per square inch and when supplemented by the secondary spring 20 that the combined resistance of thirty pounds per square inch is offered to unseating of the valve, and assuming the use of a coolant whose boiling point at sea level is approximately 220 F., then the operation of the valve from the cold closed position shown will be substantially as follows:

The first stage of operation deals with cooling system temperatures of about 220 F., or less. Under this condition the exhaust valve will always open to relieve system pressure surge at seven pounds per square inch as determined by the spring 23, because under this condition the bellows is fully contracted. As the vapor pressure builds up within the bellows the header 24 moves toward the abutment nose of the pin I! which it strikes in the neighborhood of 225 F. With bellows expansion the relief pressure will always be approximately seven pounds greater than the vapor pressure in the cooling system because any increase in pressure on the underside of the exhaust valve is now compensated for by a corresponding increase in vapor pressure in the bellows. After the header 24 contacts the pin 18 its further upward movement will be against the combined thirty pound pressure of both springs 23 and 20 and which pressure must be exceeded inorder to unseat the valve. The bellows will continue to expand as the vapor pressure builds up until the header strikes the limit stop 30 which takes place at approximately 260 F. After the bellows expansion is thus restricted further increase in vapor pressure within the bellows will not serve in holding the valveshut and therefore the further pressure build-up within the system will soon overcome the seven pound diiferential which existed just prior to the contact with stop 30 and the excess pressure will be relieved by additional compression of the blowoff springs.

From the above; description it will be seen that until the system pressure approaches the 4 given absolute relief pressure any sudden surge of pressure will be exhausted at a seven pound build-up so as to relieve the system parts from the explosive stress of violent ebullition.

We claim:

1. In a compensating safety pressure regulator for closed systems, a casing having a blowoif passage therethrough, a partition fixedly mounted in the casing, a pressure responsive expansible bellows containing a vaporized liquid and being floatingly housed by the casing on the innermost side of the fixedly mounted partition and having its inner end wall normally seated over the blow-off passage as a valve seal therefor, and a pair of tandem springs on opposite sides of the fixed partition, that on the inner side of the partition exerting its force at all times on the outer end wall of the bellows and that on the outer side of the fixed partition having its range of expansion limited by the fixed partition so as to exert its force on the outer end wall of the bellows only after a predetermined travel of said outer end wall. I

2. An atmospheric pressure and system temperature compensated safety pressure regulator for closed systems, including a valve housing open to atmosphere and having a shouldered passageway therethrough, a partition fixed therein, a pressure responsive expansible bellows containing a vaporized liquid and being iioatingly contained in said housing with its inner end wall cooperating with the shouldered passage as a closure valve therefor, spring means hearing at one end against said fixed partition and bearing at its opposite end on the outer end wall of the expansible bellows, supplementary spring means having a stop on the partition'for the free end thereof and an actuating plunger for said free end to transmit force between the supplementary spring and the last mentioned end wall of the expansible bellows only after a predetermined range of end wall movement.

3. For use with an engine cooling system, closed to atmosphere, a pressure relief device comprising a casing having a passage therethrough providing an inlet and an outlet, an expansible bellows contained fioatingly within the casing with one end cooperating with a valve seat to close said passage, a rigid bulb projected from said end with its terminal projecting through the inlet, the interior of the bulb and the bellows being open to one another and partly filled with a vaporizable liquid, a spring thrust receiving seat fixed to the other end of the bellows, a primary spring hearing at one end on said bellows thrust receiving seat and being active at all times to offer continuous spring resistances to expansion of the bellows as well as bodily movement of the bellows fromsaid valve seat, a partition plate immovably fixed on the casing and on which the opposite end of the spring bears at all times, a secondary spring active only after a predetermined deflection of the primary spring to supplement the continuous force exerted by the primary spring on said bellows, a limit stop abutment for the free end of the secondary spring bottoming on said partition plate, and a thrust transmitting pin screw threadedly mounted in said abutment for axial adjustment of pin position and projected from the abutment through said plate to terminate in position to be con-' tacted by the spring thrust receiving seat of the bellows after said predetermined deflection of the primary spring.

4. For use with an engine cooling system, closed to atmosphere, a pressure relief device comprising a casing having a passage therethrough providing an inlet and an outlet, an expansible bellows contained iloatingly within the casing with one end cooperating with a valve seat to close said passage and having a bulb projecting through the inlet, the interior of the bulb and the bellows being open to one another and partly filled with a vaporizable liquid, a spring thrust receiving seat fixed to the other end of the bellows, a primary spring bearing at one end on said bellows thrust receiving seat and being active at all times to offer continuous resistance to expansion of the bellows as well as bodily movement of the bellows away from said valve seat, apartition in the casing on which the opposite end of said spring bears and secondary spring means having one end fixed in relation to the casing and its other end free for deflection but bottoming on said partition as a limit expansion stop therefor and having a thrust mating extension for cooperation with said thrust receiving seat after predetermined deflection of the primary spring.

5. In a pressure relief device, a ported valve casing having an inlet and an outlet and a valve seat surrounding the inlet, the wall of said casing having an integral hollow offset in one side communicating with the inlet below and in bypass relation with the valve seat, an inwardly opening check valve housed Within said wall oifset, an outwardly opening valve contained within the casing for engagement with said seat, a vaporizable liquid containing expansible bellows carried by said outwardly opening valve, spring means exerting its force at all times on the bellows and acting continuously to resist expansion thereof and acting through the bellows to yieldingly seat the outwardly opening valve and additional spring means having a limited range of expansion with its deflectable free end constructed and arranged to bottom on the casing for an expansion stop and to be engaged by the bellows only after a predetermined expansion thereof for additional resistance to further expansion of the bellows and unseating of the outwardly opening valve.

JESSE E. ESHBAUGH. NELSON WALKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,705,942 Moody Mar. 19, 1929 1,737,706 Collins Dec. 3, 1929 1,737,710 Erbach Dec. 3, 1929 2,137,882 Nelson Nov. 22, 1938 2,290,059 Martin-Hurst July 14, 1942 2,335,778 Martin-Hurst Nov. 30, 1943 FOREIGN PATENTS Number Country Date 199,402 Germany June 17, 1908 

